U.S. patent number 10,649,302 [Application Number 15/306,058] was granted by the patent office on 2020-05-12 for aligned particle coating.
This patent grant is currently assigned to Hewlett-Packard Development Company, L.P.. The grantee listed for this patent is Hewlett-Packard Development Company, L.P.. Invention is credited to Doris Chun, Napoleon J Leoni.
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United States Patent |
10,649,302 |
Chun , et al. |
May 12, 2020 |
Aligned particle coating
Abstract
A method of manufacturing a coating for an e-paper assembly
includes forming a coating layer from conductive particles
dispersed within an insulative matrix. A field is applied to cause
the conductive particles to align in generally parallel, spaced
apart elongate patterns that are generally perpendicular to a plane
through which the coating layer extends. At ambient temperatures
and without applied pressure, the coating layer is cured via
radiation energy while maintaining the applied field.
Inventors: |
Chun; Doris (Santa Clara,
CA), Leoni; Napoleon J (San Jose, CA) |
Applicant: |
Name |
City |
State |
Country |
Type |
Hewlett-Packard Development Company, L.P. |
Spring |
TX |
US |
|
|
Assignee: |
Hewlett-Packard Development
Company, L.P. (Spring, TX)
|
Family
ID: |
54332941 |
Appl.
No.: |
15/306,058 |
Filed: |
April 25, 2014 |
PCT
Filed: |
April 25, 2014 |
PCT No.: |
PCT/US2014/035433 |
371(c)(1),(2),(4) Date: |
October 21, 2016 |
PCT
Pub. No.: |
WO2015/163911 |
PCT
Pub. Date: |
October 29, 2015 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20170052420 A1 |
Feb 23, 2017 |
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B05D
3/067 (20130101); B05D 3/207 (20130101); G02F
1/167 (20130101); G02F 1/16756 (20190101); G02F
2201/42 (20130101); G02F 1/16757 (20190101); G02F
1/133348 (20130101) |
Current International
Class: |
G02F
1/167 (20190101); B05D 3/00 (20060101); B05D
3/06 (20060101); G02F 1/1333 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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|
|
|
|
1469177 |
|
Jan 2004 |
|
CN |
|
103050170 |
|
Apr 2013 |
|
CN |
|
103424946 |
|
Dec 2013 |
|
CN |
|
2000149665 |
|
May 2000 |
|
JP |
|
2012022296 |
|
Feb 2012 |
|
JP |
|
Other References
Knaapila et al. "Transparency Enhancement for Photoinitiated
Polymerization (UV Curing) through Magnetic Field Alignment in a
Piezoresistive Metal/Polymer Composite" ACS Appl. Mater.
Interfaces, 2014, 6, 3469-3476. (Year: 2014). cited by examiner
.
Anisotropically Conductive Adhesives/Films (ACA/ACF). cited by
applicant .
http://link.springer.com/chapter/10.1007/978-0-387-88783-8_5
Anisotropically Conductive Adhesives/Films (ACA/ACF). cited by
applicant.
|
Primary Examiner: Walters, Jr.; Robert S
Attorney, Agent or Firm: Dicke Billig & Czaja PLLC
Claims
The invention claimed is:
1. A method of manufacturing a coating for an e-paper structure,
the method comprising: forming a first layer from a coating in
which conductive particles are dispersed within a substantially
insulative matrix, wherein forming the first layer includes
depositing the coating as the first layer onto a first side of an
e-paper substrate; applying a field to cause the conductive
particles to align in parallel, spaced apart elongate patterns that
are perpendicular to a plane through which the first layer extends;
and curing, at ambient temperatures and without applied pressure,
the first layer via radiation energy while maintaining the applied
field to produce the coating with at least a non-adhesive outer
surface.
2. The method of claim 1, comprising: providing the e-paper
substrate as an e-paper subassembly in which the first side
comprises an electrically passive, charge-responsive imageable
layer and an opposite second side comprising a counter electrode
layer, and wherein curing the first layer includes securing the
first layer to the charge-responsive imageable layer.
3. The method of claim 1, wherein the conductive particles are
magnetically responsive and the applied field is a magnetic
field.
4. The method of claim 1, wherein the particles have a conductivity
at least two orders of magnitude higher than a conductivity of the
substantially insulative matrix.
5. The method of claim 1, comprising: providing the conductive
particles to have a maximum dimension no greater than 50 .mu.m; and
arranging a viscosity of the insulative matrix to result in at
least some of the elongate patterns being spaced apart from each
other by at least 10 .mu.m.
6. A method of manufacturing an e-paper structure comprising:
providing an e-paper structure including an electrically passive,
imageable layer having a first side and an opposite second side
onto which is fixed a counter electrode layer; depositing a coating
onto the first side of the imageable layer, the coating including
conductive particles dispersed within a conductive-resistant medium
which is non-adhesive upon curing; applying a field to cause the
conductive particles within the coating to align in parallel,
spaced apart elongate patterns that are perpendicular to a plane
through which the imageable layer extends; and curing, at ambient
temperatures and without applied pressure, the coating via
radiation energy while maintaining the applied field.
7. The method of claim 6, wherein the conductive particles include
a magnetically-responsive material and the field is a magnetic
field.
8. The method of claim 7, wherein the magnetically-responsive
material includes at least one of pure transition metals, pure
lanthanides, transition metal oxides, lanthanide oxides, and
complexes of metals from the transition metals and lanthanides.
9. The method of claim 7, comprising: providing the conductive
particles with a first conductivity at least two orders of
magnitude greater than a second conductivity of the
conductive-resistant medium, wherein the elongate patterns of
conductive particles collectively define a third conductivity, and
wherein the second conductivity of the conductive-resistant medium
is at least one order of magnitude less than the third
conductivity.
10. The method of claim 6, comprising: providing the conductive
particles to have a maximum dimension no greater than 50 .mu.m;
selecting a viscosity of the conductive-resistant medium to result
in at least some of the elongate patterns having a width no greater
than 25 .mu.m and at least some of the elongate patterns being
spaced apart from each other by at least 10 .mu.m; and arranging
the coating to have a thickness of about 50 to about 200 .mu.m.
11. A method of manufacturing an e-paper structure comprising:
providing an e-paper structure including a charge-responsive layer
having a first side and an opposite second side onto which is fixed
a counter electrode layer; depositing a coating as an outer
protective layer onto the first side of the charge-responsive
layer, the coating including conductive particles dispersed within
a cohesive, insulative matrix which is non-adhesive upon curing,
wherein the conductive particles have a first conductivity at least
two orders of magnitude greater than a second conductivity of the
insulative matrix and wherein the conductive particles include a
magnetically-responsive material; applying a field to cause the
conductive particles within the outer protective layer to align in
parallel elongate patterns to extend in a first orientation
perpendicular to a plane through which the charge-responsive layer
extends; and curing, at ambient temperatures and without applied
pressure, the outer protective layer via radiation energy while
maintaining the applied field.
12. The method of claim 11, comprising: limiting a duration of
application of the field to cause each elongate pattern of
conductive particles to form a series of staggered segments, with
each segment aligned parallel to the first orientation.
13. The method of claim 11, wherein the insulative matrix includes
a UV-curable polymer and the radiation energy falls within the UV
wavelengths.
Description
BACKGROUND
Electronic paper ("e-paper") is a display technology designed to
recreate the appearance of ink on ordinary paper. Some examples of
e-paper reflect light like ordinary paper and may be capable of
displaying text and images. Some e-paper is implemented as a
flexible, thin sheet, like paper. One familiar e-paper
implementation includes e-readers.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1A is a sectional view schematically representing a
charge-receiving layer, according to an example of the present
disclosure.
FIG. 1B is a sectional view schematically representing a
charge-receiving layer, according to an example of the present
disclosure.
FIG. 2A is a sectional view schematically representing a
charge-receiving layer, according to an example of the present
disclosure.
FIG. 2B is a sectional view schematically representing a
charge-receiving layer, according to an example of the present
disclosure.
FIG. 3A is a sectional view schematically representing an e-paper
assembly, according to an example of the present disclosure.
FIG. 3B is an enlarged sectional view of a portion of FIG. 3A that
schematically represents a portion of an e-paper assembly,
according to an example of the present disclosure.
FIG. 3C is an enlarged sectional view schematically representing a
portion of an e-paper assembly, according to an example of the
present disclosure.
FIG. 3D is a perspective view schematically representing a coating
layer, according to an example of the present disclosure.
FIG. 4A is a top elevational view schematically representing a
display media, according to an example of the present
disclosure.
FIG. 4B is a top view schematically representing a dot-by-dot
portion of an image, according to an example of the present
disclosure.
FIG. 5 is a diagram including a sectional side view schematically
representing an e-paper assembly, according to an example of the
present disclosure.
FIG. 6 is a diagram including a sectional side view schematically
representing an e-paper assembly and a side view of an imaging
head, according to an example of the present disclosure.
FIG. 7 is a diagram including a sectional side view schematically
representing an e-paper assembly and a side view of an imaging
head, according to an example of the present disclosure.
FIG. 8 is a diagram including a sectional side view schematically
representing an e-paper assembly and a side view of an imaging
head, according to an example of the present disclosure.
FIG. 9 is a diagram including a flow diagram schematically
representing a method of forming a coating layer, according to an
example of the present disclosure.
FIG. 10 is a diagram including schematically representing a portion
of a method of forming a coating layer, according to an example of
the present disclosure.
DETAILED DESCRIPTION
In the following detailed description, reference is made to the
accompanying drawings which form a part hereof, and in which is
shown by way of illustration specific examples in which the
disclosure may be practiced. It is to be understood that other
examples may be utilized and structural or logical changes may be
made without departing from the scope of the present disclosure.
The following detailed description, therefore, is not to be taken
in a limiting sense.
At least some examples of the present disclosure are directed to a
coating layer that protects an e-paper structure while also acting
as a charge-receiving layer to receive airborne charges from a
non-contact, external image-writing module and facilitate passage
of those charges to a charge-responsive layer of the e-paper
structure. In one aspect, the coating layer exhibits anisotropic
conductivity to facilitate passage of the airborne charges in a
first orientation through a thickness of the coating layer while
inhibiting migration of those charges in a second orientation
generally perpendicular to first orientation. In one aspect, the
second orientation is generally parallel to a plane through which
the coating layer extends. The coating layer also has a thickness
and/or composition that provides scratch resistance, strength, and
toughness to protect the e-paper structure from mechanical insults.
In some examples, other aspects of the coating layer provide
protection from electrical insults, as further described later.
In some examples, a charge-receiving layer for an electronic paper
assembly includes a plurality of conductive paths spaced apart
throughout an electrically insulative matrix (e.g. a
conductive-resistant medium). Each conductive path includes at
least one elongate pattern of separate conductive particles. In one
aspect, each conductive path extends in a first orientation
generally perpendicular to a plane through which the
charge-receiving layer extends and a plane through which the
charge-responsive layer extends. In some examples, the conductivity
of any single elongate pattern of conductive particles is at least
two orders of magnitude greater than a conductivity of the
insulative matrix. In some examples, a combined conductivity of all
the conductive paths is about one order of magnitude greater than a
conductivity of the insulative matrix.
It will be understood that the term "insulative matrix" does not
indicate that the matrix is an absolute electrical insulator, but
rather that the matrix is electrically insulative at least relative
to the conductivity of the conductive paths (of elongate patterns
of conductive particles). Further examples of the insulative matrix
are described throughout the present disclosure.
With such arrangements provided via at least some example of the
present disclosure, charges deposited on a surface of the
charge-receiving layer can travel in generally direct alignment
with a targeted area of the charge-responsive layer (of an e-paper
structure) to be imaged.
In sharp contrast, unprotected e-paper will not survive the rigors
of use in practical consumer and business applications. In further
sharp contrast to at least some examples of the present disclosure,
other types of protective coatings which exhibit nearly perfect
dielectric behavior (e.g. glass, some polymers) tend to produce
"dot blooming" because any charges deposited on the surface of the
protective layer tend to build up at the surface of the protective
coating and spread laterally far beyond the targeted area. This
surface spreading, in turn, results in lateral spreading of the
imaged area in the charge-responsive layer of the e-paper
structure, thereby reducing the clarity and resolution of the
image.
In further sharp contrast to at least some examples of the present
disclosure, other types of protective coatings exhibit
semi-conductive behaviors and therefore permit passage of charges
through a thickness of the protective coating to a
charge-responsive layer. However, the isotropic nature of the
semi-conductive protective coatings still results in a "dot
blooming" effect because as the charges travel through the
semi-conductive material, the charges spread laterally so that by
the time the charges reach the targeted image area, the charges
affect an much larger than intended area of the charge-responsive
layer. This behavior can result in poor image quality.
However, with at least some examples of the present disclosure,
some of which are introduced above, even with relatively thick
protective coatings (e.g. 150 .mu.m), an anisotropic conductive
configuration in the charge-receiving layer prevents lateral
migration of deposited charges. Accordingly, high quality imaging
is achieved while providing the desired protection for the e-paper
structures.
In at least some examples of the present disclosure, a method of
manufacturing an outer coating for an e-paper structure includes
forming a first layer from a mixture of conductive particles
dispersed within an insulative matrix. A field is applied to cause
the conductive particles to align in generally parallel, spaced
apart elongate patterns that are generally perpendicular to a plane
through which the layer extends. In some examples, the applied
field is a magnetic field and the particles are
magnetically-responsive particles. In some examples, the applied
field is an electric field.
In some examples, the method further includes curing, at ambient
temperatures and without applied pressure, the first layer via
radiation energy while maintaining the applied field.
In one aspect, at least an outer surface of the protective outer
coating (for the e-paper structure) that is exposed to the ambient
environment is non-adhesive or non-sticky.
In sharp contrast to at least some examples of the present
disclosure, at least some types of anisotropic conductive films
(ACF) act as adhesive interconnects for circuitry components and
therefore do not serve well as outer protective coatings generally,
and particularly for a charge-responsive layer of an e-paper
structure. Moreover, deployment of such types of anisotropic
conductive films (ACF) typically involves the application of high
heat and/or pressure, which would be destructive to the delicate
nature of passive e-paper structures.
In addition, such types of anisotropic conductive films typically
rely on a monolayer of metal spheres which define the thickness of
the film. Accordingly, attempts to create relatively thick
protective films (e.g. 150 .mu.m) would involve films with large
diameter spheres, and typically result in large spacing (e.g. 150
.mu.m) between the conductive spheres. This arrangement, in turn,
would result in a poor mismatch between the large spaces between
adjacent conductive spheres relative to the closely adjacent
microcapsules of the passive e-paper structure, leading to poor
image quality. In another aspect, traditional anisotropic
conductive films typically used as circuitry interconnects also
exhibit impedances on the order of Ohms.
In sharp contrast, in at least some examples of the present
disclosure the insulative matrix exhibit impedances in hundreds of
kiloOhms (e.g. 10.sup.5 to 10.sup.9 Ohms) while each preferential
conductive path exhibits impedances about two orders of magnitude
less than the insulative matrix. In this environment, in at least
some examples of the present disclosure, a current density
associated with deposited air-borne charges and the above-described
preferential conductive charge-receiving layer falls within a range
of 10 to 100 .mu.A/cm.sup.2.
In at least some further examples of the present disclosure, the
conductive particles have a maximum dimension no greater than 5
.mu.m. In some examples, the generally parallel elongate patterns
(of conductive particles) are spaced apart from each other by about
10 .mu.m. In some examples, the conductive particles have a maximum
dimension no greater than 100 nanometers. In some examples, the
conductive particles have a maximum dimension no greater than 10
nanometers. Other examples are described later.
In some examples, the conductive particles are sized such that each
elongate pattern of aligned particles comprises a mono-layer in
which a width of a respective elongate pattern corresponds to a
maximum dimension of a respective one of the conductive particles.
In some examples, the conductive particles have a relatively
smaller size such that each elongate pattern of aligned particles
comprises a multi-layer in which a width of each elongate pattern
corresponds to multiple layers of the conductive particles.
Moreover, an e-paper structure (according to at least some examples
of the present disclosure) forms at least a portion of a passive
e-paper display media. The passive e-paper display media is
relatively thin and light because it omits a power supply and omits
internal circuitry, thereby giving the passive e-paper display
media a look and feel more like traditional paper. The passive
e-paper display media in at least some examples of the present
disclosure relies on a charge-responsive layer that is imageable
via an external writing module and that does not require a power
supply to be imaged or to retain an image.
In sharp contrast, traditional e-paper implementations include
active e-paper structures having internal circuitry and/or an
on-board power supply, making them relatively heavy and not feeling
like traditional paper.
These examples, and additional examples, are described and
illustrated below in association with at least FIGS. 1A-10.
FIG. 1A is a side sectional view schematically representing a
coating layer 20, according to an example of the present
disclosure. In one example, the coating layer 20 provides
protection for an e-paper structure (shown later in at least FIGS.
3A, 5-8).
As shown in FIG. 1A, coating layer 20 includes a first side 22A and
an opposite second side 22B, as well as opposite ends 26A, 26B. In
one example, coating layer 20 includes a body 30 in which is formed
a plurality of conductive pathways 32. In one aspect, a
longitudinal axis (A1) of the conductive paths 32 extends generally
perpendicular to a longitudinal axis (A2) the body 30. In one
example, in contrast to conductive paths 32, body 30 includes an
insulative matrix 33 (e.g. conductive-resistant medium).
In one example, the conductivity (.sigma..sub.path) of a single
conductive path 32 is at least two orders of magnitude greater than
the conductivity (.sigma..sub.body) of body 30. In some examples, a
combined conductivity of all the conductive paths 32 in coating
layer 20 is at least one order of magnitude greater than the
conductivity (.sigma..sub.body) of body 30.
As further shown in FIG. 1A, coating layer 20 is adapted to receive
air-borne charges 39 from an external imaging head (not shown) that
is spaced apart from and not in contact with the coating layer 20.
In one aspect, due to the relatively low conductivity of body 30,
charges that are generally received on body 30 are conducted
laterally through the outer surface of body 30 until they reach a
conductive pathway 35 while charges received at a conductive
pathway 35 travel straight (i.e. directly) through a thickness of
the coating layer 20. In particular, the relatively high
conductivity of conductive paths 32 facilitates passage of the
charges (through layer 20) from the first side 22A to the second
side 22B.
In some examples, when coating layer 20 forms part of a larger
e-paper assembly, coating layer 20 acts as a charge-receiving layer
to facilitate receiving charges from an external location/source
and conveying those charges to a charge-responsive layer of the
e-paper assembly. This configuration is illustrated later in
association with at least FIGS. 3A and 5-8.
In one example, for illustrative purposes, FIG. 1A does not depict
a particular density of conductive paths 32 relative to body 30.
Rather, the coating layer 20 in FIG. 1A is merely illustrative for
describing general principles in at least some examples of the
present disclosure, such as the orientation and/or conductivity of
the paths 32 relative to body 30.
FIG. 1B is a side sectional view of a coating layer 40, according
to one example of the present disclosure. In some examples, coating
layer 40 is at least consistent with, and/or includes at least some
of substantially the same features and attributes as, coating layer
20 in FIG. 1A. In coating layer 40, a plurality of conductive paths
extend from first side 22A to second side 22B with each conductive
path being defined by at least one elongate pattern 56 of
conductive particles 58. Each conductive path facilitates the
passage of charges from first side 22A to second side 22B.
In some examples, as shown in FIG. 1B, a conductive path 53
corresponds to a single elongate pattern 56 of conductive particles
58 while in some examples, a conductive path 52 corresponds to at
least two adjacent elongate patterns 56 of conductive particles
58.
In one example, the conductivity (.sigma..sub.path) of a single
elongate pattern 56 of conductive particles 58 is at least two
orders of magnitude greater than the conductivity
(.sigma..sub.body) of body 30 of insulative matrix 33 at the
relevant electrical fields used for imaging.
In some examples, the number of adjacent elongate patterns 56 of
conductive particles 58 that defines a conductive path 52
corresponds to a size of an imageable dot in dot-based imaging
scheme. For instance, in one example implementation involving an
image with 300 dots-per-inch density on a media, a dot is about 80
to 100 microns in diameter with the dots spaced apart by 84
microns. In such an implementation, as further described below in
association with at least FIGS. 4A-4B, several elongate patterns 56
of conductive particles 58 define the conductive path 52 to cause
imaging of a single dot on a charge-responsive layer of an e-paper
assembly.
In one example, particles 58 are at least partially made of a
field-responsive material that is alignable into the elongate
patterns 56 during formation of the coating layer 40. With this in
mind, FIG. 2A provides a brief introduction into the process of
forming the elongate patterns 56 of separate conductive particles
58 within body 30. In particular, as shown in FIG. 2A, a fluid
mixture of at least insulative matrix 33 (e.g. conductive-resistant
medium) and conductive particles 58 is formed as a layer 80 on a
substrate, such as but not limited to, an e-paper assembly. Upon
initial deposit, the particles 58 within the layer 80 are randomly
and generally dispersed throughout the insulative matrix 33. Prior
to curing of the layer 80, a field (AF) is applied to the layer 80
with an orientation to cause the conductive particles 58 to become
aligned with the field lines (F) of the applied field (AF), to
result in the arrangement shown in FIG. 1B, in which the particles
58 remain separate particles but become aligned into elongate
patterns 56 that are generally parallel to each other and spaced
apart from each other, as shown in FIG. 1B. In some examples, once
aligned into an elongate pattern 56, some particles 58 (of a
particular elongate pattern 56) contact each other while some
particles (of that same elongate pattern 56) are spaced apart from
each other. Once in the arrangement shown in FIG. 1B, at least
layer 80 is cured in a manner such that the particles 58 will
remain in the arrangement shown in FIG. 1B.
In one example, the conductive particles 58 include a
magnetically-responsive material and the applied field is a
magnetic field.
Further details regarding the type of material comprising the
particles and regarding a process of arranging the particles 58
into elongate patterns 56 are described later in association with
at least FIGS. 9-10.
FIG. 2B is a sectional view schematically representing a
charge-receiving layer 90, according to one example of the present
disclosure. In some examples, charge-receiving layer 90 is at least
consistent with and/or includes at least substantially the same
features and attributes as charge-receiving layer 40 (as previously
described in association with FIG. 1B), except for providing
elongate patterns 102 of conductive particles 58 (forming
conductive paths 100) in which the conductive particles 58 are not
aligned in a strictly linear pattern. Instead, the particles 58
vary in their position along the X plane (represented by
directional arrow X) by a small distance, but with substantially
all of the particles 58 (of one elongate pattern 102) falling
between boundaries B1 and B2 (for one conductive path 100), and
between B3 and B4 (for another conductive path 100), respectively.
In addition, despite the variable spacing along the X plane, the
conductive particles 58 still form elongate patterns 102 that have
a longitudinal axis (A1) that extends generally perpendicular to a
longitudinal axis (A2) of the charge-receiving layer 90.
In some examples, some conductive paths 100 include an end particle
61 directly exposed at first side 22A, while in some examples, some
conductive paths 100 include an end particle 59 recessed from (i.e.
spaced apart) first side 22A by a gap G1, as shown in FIG. 2B. As
further demonstrated via FIG. 2B, in some examples at least some of
the conductive particles, such as 63, 64 are spaced apart from each
other (represented by gap G2) along a first orientation generally
parallel to the longitudinal axis (A1) of the elongate pattern 102.
In this latter aspect, in some examples the particles 58 (such as
63, 64) do not form a contiguous structure or monolithic structure,
but instead define an elongate band or elongate pattern of separate
particles adapted to provide a conductive path to convey (i.e.
facilitate migration) of charges. In some examples, the spacing
(e.g. G2) along the Y orientation or in the X plane is
non-uniform.
FIG. 3A is a diagram 130 including a side sectional view
schematically representing an e-paper structure 132 and an
associated e-paper writing module 160, according to one example of
the present disclosure. In some examples, e-paper structure 132 is
consistent with, and/or includes at least some of substantially the
same features and attributes as e-paper display media previously
described in association with at least FIGS. 1A-2. Meanwhile,
writing module 160 is provided in FIG. 3A to generally illustrate a
response of the e-paper structure 132 to air-borne charges emitted
from an erasing unit 166 and/or a writing unit 164.
As shown in FIG. 3A, the writing module 160 includes writing unit
164 and an erasing unit 166. The writing unit 164 and erasing unit
166 both face a charge receiving surface 192 of the media, with the
writing module 160 spaced apart from the surface 192. In some
examples, this external writing module 160 is spaced apart (at
least during erasing and/or writing) from the charge-receiving
layer 138 by a distance of 125 .mu.m to 2 millimeters.
In some examples, one or both of the writing unit 164 and erasing
unit 166 comprises an ion-based head. In one example, the ion-based
head is provided via a corona-based charge ejecting device. In some
examples, an ion-based erasing unit 166 is replaced with an
electrode that comes into close contact with, or that is dragged
along, the surface 192 in front of the writing unit 164. As
represented by arrow R, erasing and writing is performed upon
relative movement between the writing module 160 and the e-paper
structure 132.
In some examples, a surface 192 is sometimes referred to as an
imaging side of the e-paper structure 132 and an opposite surface
190 is sometimes referred to as a non-imaging side of the e-paper
structure 132.
In general terms, as shown in FIG. 3A, e-paper structure 132
includes a protective layer 138, a charge-responsive layer 139, and
a base 140. The protective layer 138 is sometimes referred to as
charge-receiving layer 138. The base 140 defines or includes a
counter electrode, as further described below, which serves as a
ground plane. In some examples, it will be understood that, even in
the absence of layer 138, charge-responsive layer 139 is imageable
by charges 39 and that layer 138 primarily is provided for
protection of unintentional and/or malicious mechanical and
electrical insults to charge-responsive layer 139. Nevertheless, in
at least some examples of the present disclosure, the presence of
the protective layer 138 facilitates producing and retaining
quality images at charge-responsive layer 139 in the manner
described herein.
In some examples, charge-receiving layer 138 is consistent with,
and/or includes at least some of substantially the same features
and attributes as layers 20, 40 (FIGS. 1A-2). In particular, as
shown in FIG. 3A, charge-receiving layer 138 includes a plurality
of generally parallel, spaced apart conductive paths 185, with each
conductive path formed from an elongate pattern of separate
conductive particles 188. As shown in the enlarged portion A of
FIG. 3A, the conductive particles 188 are generally arranged in
series.
Furthermore, it will be understood that particles 188 are not
limited to the shapes shown in portion A of FIG. 3A and the shape
of the particles 188 can vary depending on the type of material
forming particles 188 and/or depending on the processing of the
materials forming particles 188.
With further reference to at least FIG. 3A and consistent with at
least FIG. 2B, in some examples, each conductive path 185 has a
width or diameter (D3) with adjacent conductive paths 185 being
spaced apart by a distance D2. In some examples, the spacing (D2)
between adjacent conductive paths 185 is about 10 .mu.m and can
fall within range between 5 to 15 .mu.m. Meanwhile, the width (D3)
of the conductive paths 185 generally falls within a range between
2 and 6 .mu.m, with the width (D3) depending on the viscosity of
the insulative matrix 33 in which the conductive paths 185 are
dispersed.
However, in some examples, the width (D3) of at least some
conductive paths 185 is no greater than 25 .mu.m.
In some examples, the protective or charge-receiving layer 138 has
a thickness of about 10 .mu.m to about 200 .mu.m. In some examples,
the charge-receiving layer 138 has a thickness of about 50 .mu.m to
about 175 .mu.m. In some examples, the charge-receiving layer 138
has a thickness of about 150 .mu.m.
In some examples, the charge-receiving layer 138 has a thickness
that is a multiple (e.g. 2.times., 3.times., 4.times.) of a
thickness of a charge-responsive layer 139 to ensure robust
mechanical protection of the charge-responsive layer 139. In one
aspect of such examples, a thickness of the charge-responsive layer
139 generally corresponds to a diameter of microcapsules 145
(forming a monolayer).
In one aspect, the thickness and type of materials forming
charge-receiving layer 138 are selected to mechanically protect the
charge-responsive layer 139 (including microcapsules 145) from
punctures, abrasion, bending, scratching, liquid hazards, crushing,
and other impacts. Moreover, as further described later, in some
examples the layer 138 also protects the charge-responsive layer
139 from tribo charges.
In addition, by providing preferential conductivity,
charge-receiving layer 138 reduces unintentional increases in image
dot size that might otherwise occur due to a blooming effect, as
previously described.
In the example shown in FIG. 3A, the charge-responsive layer 139
includes a plurality of microcapsules 145 arranged in a monolayer.
Each microcapsule 145 encapsulates some charged black particles 154
and some charged white particles 150 dispersed within a matrix 141,
such as a dielectric liquid (e.g. an oil). In one example, as shown
in at least FIGS. 3A and 5-8, the black particles 154 are
positively charged and the white particles 150 are negatively
charged while the erasing unit 166 produces negative charges and
the writing unit 164 produces positive charges.
In some examples, the erasing unit 166 erases any information
stored via the microcapsules 145 prior to writing information with
the writing unit 164. In the example shown in FIG. 3A, upon
relative motion between the e-paper structure 132 and the writing
module 160, the negatively charged erasing unit 166 emits a stream
of air-borne charges 41, which will result in removal of positively
charged ions that are attached to the surface 147 of
charge-responsive layer 139, as further illustrated in the enlarged
view of FIG. 3B. The negatively charged erasing unit 166 also
creates electrostatic forces that drive negatively charged white
particles 150 away from the charge receiving layer 138 and attracts
positively charged black particles 154 toward the charge receiving
layer 138. By passing the erasing unit 166 over the charge
receiving layer 138, any information previously written to the
e-paper structure 132 is erased by positioning the positively
charged black particles 154 near the top of the microcapsules 145
and pushing the negatively charged white particles 150 to the
bottom of the microcapsules 145.
It will be understood that depending on whether a particular side
192 or 190 of e-paper structure 132 is opaque or transparent, a
respective side 192 or 190 can be a viewing side or non-viewing
side of the e-paper structure, as will be further noted later.
However, regardless of which side 192 or 190 is a viewing side,
side 192 will remain an imaging side of the e-paper structure
132.
Microcapsules 145 exhibit image stability using adhesion between
particles and/or between the particles and the microcapsule
surface. For example, microcapsules 145 can hold text, graphics,
and images indefinitely without using electricity, while allowing
the text, graphics, or images to be changed later.
In some examples, the diameter (D1) of each microcapsule 145 is
substantially constant within charge-responsive layer 139 of
e-paper structure 132 and, in some examples, the thickness (H1) of
charge-responsive layer 139 is between about 20 .mu.m and about 100
.mu.m, such as 50 .mu.m. In some examples, the charge-responsive
layer 139 is arranged as a monolayer and has a thickness of
generally corresponding to a diameter (D1) of the microcapsules,
which in some examples, is about 30 to 40 .mu.m.
In some examples, base 140 has a thickness between about 20 .mu.m
and about 1 mm, or larger depending on how e-paper structure 132 is
to be used.
In one aspect, base 140 is structured to provide enough
conductivity to enable counter charges to flow during printing. As
such, in general terms, base 140 comprises a member including at
least some conductive properties. In some examples, base 140
comprises a non-conductive material that is impregnated with
conductive additive materials, such as carbon nanofibers or other
conductive elements. In some examples, base 140 comprises a
conductive polymer, such as a urethane material or a carbonite
material. In further examples, base 140 is made from a conductive
polymer with carbon nanofibers, to provide flexibility with
adequate strength.
In some examples, base 140 is primarily comprised of a conductive
material, such as an aluminum material and therefore is impregnated
or coated with additional conductive materials.
In some examples, whether conductivity is provided via coating,
impregnation or other mechanisms, the body of base 140 is formed
from a generally electrically insulative, biaxially-oriented
polyethylene terephthalate (BOPET), commonly sold under the trade
name MYLAR, to provide flexibility and strength in a relatively
thin layer.
As noted elsewhere throughout the present disclosure, the base 140
is opaque or is transparent, depending on the particular
implementation of the e-paper display media. In some examples, the
base 140 comprises a generally resilient material, exhibiting
flexibility and in some implementations, semi-rigid behavior. In
some examples, the base 140 comprises a rigid material.
FIG. 3A also shows one example of a writing operation performed by
the writing module 160 in which the deposition of charges within
target zone Z (between dashed lines Z1, Z2) influences the
distribution of charged pigments/particles within affected
microcapsules 145. In one aspect, in order to form an image on
e-paper structure 132, the writing unit 164 is designed and
operated to selectively eject positive charges 39 toward the
surface 192 of charge-receiving layer 138, when a region of the
e-paper structure 132 (located beneath the writing unit 164) is to
be changed from white to black (or vice versa in some examples). As
noted above, conductive paths 185 extending through the
charge-receiving layer 138 (between opposite sides 172A, 172B)
facilitate passage of the deposited charges to the
charge-responsive layer 139. It will be understood that the passage
of charges 39 through charge-receiving layer 138 is limited to
those locations (e.g. within target zone Z) at which charges were
intentionally deposited by writing module 160.
In this example, as a resulting effect from the deposit of the
positive charges 39 at charge-receiving layer 138, the positively
charged black particles 154 (within the nearby microcapsules 145)
are repelled and driven away from the surface 147 of
charge-responsive layer 139, while the negatively charged white
particles 150 (within nearby microcapsules 145) are attracted to
the positive charges 39 and pulled toward the charge receiving
surface 147, as further illustrated in the enlarged view of FIG.
3B.
In some examples, when at least a portion of base 140 is
transparent and surface 190 comprises a viewing side of the e-paper
structure 132, the areas of surface 147 having a positive charge
will result in the microcapsules 145 (or portions of a microcapsule
145) producing a black appearance at surface 190 while the areas of
surface 147 having negative charge will result in corresponding
microcapsules 145 (or portions of a microcapsule 145) producing a
white appearance at surface 190. In some instances of this example,
the charge-receiving layer 138 is opaque to facilitate clarity in
viewing through transparent base 140 at surface 190. Accordingly,
in this implementation, the charge-receiving layer 138 serves as an
imaging side, but is a non-viewing side of the e-paper structure
132.
On the other hand, in some examples, when at least a portion of
charge-receiving layer 138 is transparent and surface 192 comprises
a viewing side of the e-paper structure 132, the areas of surface
147 having a positive charge will result in the microcapsules 145
(or portions of a microcapsule 145) producing a white appearance at
surface 192 while the areas of surface 147 having negative charge
will result in corresponding microcapsules 145 (or portions of a
microcapsule 145) producing a black appearance at surface 192. In
some instances of this example, the base 140 is opaque to
facilitate clarity in viewing through transparent charge-receiving
layer 138 at surface 192. Accordingly, in this implementation, the
charge-receiving layer 138 serves as both an imaging side and a
viewing side of the e-paper structure 132.
In some examples, as shown in FIG. 3A, during writing and erasing
electrical contact is made by a ground resource (GND), associated
with writing module 160, with exposed portions of base 140 to allow
biasing of the writing module 160 while it directs charges to
charge receiving layer 138 during the writing process.
The e-paper writing module 160, as shown in FIG. 3A, is not limited
to implementations in which the writing unit 164 produces positive
charges and the erasing unit 166 erases information with negative
charges. Instead, in some examples, the microcapsules 145 in matrix
material 141 of the charge-responsive layer 139 of e-paper
structure 132 are composed of negatively charged black particles
154 and positively charged white particles 150. In such examples,
the writing unit 164 is designed to produce negative charges (e.g.
negatively charged ions), while the erasing unit 166 uses positive
charges to erase information stored in the microcapsules 145 of the
charge-responsive layer 139 of the e-paper structure 132.
In one aspect, it will be understood that in at least some examples
of the present disclosure, the e-paper structure 132 operates
without an applied voltage at surface 192 (e.g. side 172A of layer
138) and without an electrically-active conductive element in
contact with surface 192. Instead, via the presence of the counter
electrode 140 (e.g. base) and the established ground path,
air-borne charges produced via writing module 160 arrive at surface
192 and flow to charge-responsive layer 139 through targeted
preferential conductive paths in charge-receiving layer 138.
With reference to the enlarged view of FIG. 3C as taken from FIG.
3A (represented by marker C), in some examples in which conductive
particles 188 are magnetically responsive, an insulative matrix 243
of a charge-receiving layer further includes a plurality 245 of
non-magnetically-responsive conductive elements 247 dispersed
throughout the insulative matrix 243, such as between the
conductive paths 185 (made of magnetically-responsive particles
188). It will be understood that for illustrative purposes,
conductive elements 247 are not necessarily shown to scale in FIG.
3C. In some examples, the conductive elements 247 slightly augment
the conductivity of the insulative matrix 243 to provide
anti-static, protective qualities without otherwise disrupting the
anisotropic conductivity provided via the conductive paths. In
other words, while the conductive paths 185 facilitate passage of
intentionally deposited charges from writing module 160 (FIG. 3A),
the non-magnetic conductive elements 247 act as a secondary charge
dissipation mechanism for residual and/or tribo charges on surface
192 of the e-paper structure. In this way, the non-magnetic
conductive elements help to prevent inadvertent disturbance of an
image formed at charge-responsive layer 139 of e-paper structure
132 (FIG. 3A), and their presence contributes to the stability and
clarity of an image written to charge-responsive layer 139 of
e-paper structure 132. In one aspect, because the conductive
elements 247 are non-magnetically-responsive, their location is
unaffected during formation of the charge-receiving layer 138 when
particles 188 are subjected to a magnetic field to cause their
alignment into conductive paths 185.
FIG. 3D is a diagram 250 including a perspective view schematically
representing a portion of a charge-receiving layer 260 of an
e-paper structure, according to an example of the present
disclosure. In one example, the charge-receiving layer 260 is
consistent with, and/or includes at least some of substantially the
same features and attributes, as charge-receiving layer 138 as
previously described in association with at least FIGS. 3A-3C. As
shown in FIG. 3D, the example portion of the charge-receiving layer
260 includes a plurality 280 of conductive paths 285 with each
conductive path 285 formed via magnetically-alignable conductive
particles. The example portion exhibits a height (H2) in the
z-direction and in the x-y direction, has a width (D4) and length
(D5). Among other attributes, FIG. 3D illustrates a relative
density of the conductive paths 285 within a given portion of the
charge-receiving layer 138. In some examples, the density of
conductive paths 285 is at least partly controllable based on a
viscosity of the insulative matrix 287.
It will be understood that the conductive paths 285 are shown in
FIG. 3D resembling columnar structures solely for illustrative
simplicity to depict geometric and spatial relationships for a
charge-receiving layer, and that the conductive paths 285 would
actually be implemented via elongate patterns of separate
conductive particles, as previously described in at least FIGS. 1B,
2B, 3A, etc.
FIG. 4A is top plan view schematically representing a portion of an
e-paper display media 300, according to an example of the present
disclosure. As shown in FIG. 1A, display media 300 includes
image-bearing face 330.
As further described below in more detail, e-paper display media
300 incorporates e-paper structure like e-paper structure 132 as
previously described in association with at least FIG. 3A.
Accordingly, in some examples, the image-viewable surface (i.e.
image-bearing surface) 330 corresponds to the image-writing surface
(e.g. surface 192 in FIG. 3A) of the e-paper display media 300
while in some examples, the image-viewable surface (i.e.
image-bearing surface) corresponds to a non-image-writable surface
(e.g. surface 190 in FIG. 3A) of the e-paper display media 300.
As shown in FIG. 4A, in some examples e-paper display media 300
bears an image 340. In some examples, image 340 includes text 344
and/or graphics 348 positioned among the remaining blank portion
350. It will be understood that in this context, in some examples,
graphics also refers to an image, such as specific picture of a
person, object, place, etc. Moreover, the particular content of the
information in image 340 is not fixed, but is changeable by virtue
of the rewritable nature of the e-paper structure 132 incorporated
within display media 300. In one example, a location, shape, and/or
size of text 344 and/or graphics 348 of an image 340 is also not
fixed, but is changeable by virtue of the rewritable nature of the
e-paper display media 300.
In at least some examples of the present disclosure, an e-paper
structure (e.g. e-paper structure 132 in FIG. 3A) forming at least
a portion of display media 300 is a passive e-paper display. In one
aspect, the e-paper display 300 is passive in the sense that it is
re-writable and holds an image without being connected to an active
power source during the writing process and/or after the writing is
completed. Instead, as previously described, the passive e-paper
structure 132 is imaged in a non-contact manner in which the
e-paper display 300 receives charges (emitted by a ion head) that
travel through the air and then forms the image 340 via a response
by charged particles within the charge-responsive layer 139 of the
e-paper structure 132. After the imaging process is completed, the
passive e-paper display 300 retains the image generally
indefinitely and without a power supply until image 340 is
selectively changed at a later time.
In some examples, an e-paper structure forming display media 300
and that includes a charge-receiving layer (such as
charge-receiving layer 138 in FIG. 3A or in later FIGS. 5-8) is not
strictly limited to the particular type of charge-responsive layer
139 previously described in association with at least FIG. 3A.
Rather, in some examples, the charge-responsive layer forming an
e-paper assembly (onto which a charge-receiving layer according to
at least some examples of the present disclosure) operates at least
consistent with general electrophoretic principles. With this in
mind, in some examples, such charge-responsive layers include
charged color particles (other than microcapsules 145) that switch
color when charges are selectively applied a non-contact manner by
an external writing module. In some examples, the charged color
particles comprise pigment/dye components.
In some examples, an e-paper structure incorporated within display
media 300 is constructed via placing celled structures between two
containing walls. In some examples, an e-paper structure
incorporated within display media 300 includes air borne particles
insides capsules, such as a "quick response liquid powder display"
formerly available from Bridgestone Corporation of Tokyo,
Japan.
With further reference to FIG. 4A, in some examples, the image 340
appearing on face 330 of display media 300 results from writing the
image at resolution of 300 dots-per-inch. In some examples, image
340 is written at greater or less resolutions than 300
dots-per-inch.
With this in mind, FIG. 4B is a diagram 375 including a top plan
view of a portion 378 of image 340, according to one example of the
present disclosure. As shown in FIG. 4B, diagram 375 includes a
layout 380 of dots 382, each of which can be written as black dots
or white dots based on a response of the underlying e-paper
structure 132 to deposited charges selectively targeted in a manner
corresponding to the pattern of image 340. As shown in FIG. 4B, the
portion 378 of image 340 includes some white dots 382A and some
black dots 382B. The white dots 382A appear as blank portion 350 in
image 340 shown in FIG. 4A, while the black dots 382B appear as a
portion of text 344, graphic 348, etc. A center-to-center spacing
between dots 382 is represented by distance D6 while a diameter of
each dot 382 is represented by distance D7. In one example, to
achieve a 300 dpi image, the distance D6 is 84 microns and the
diameter (D7) of each dot 382 is about 80 to 100 microns.
With this in mind, in some examples, a black dot 382B typically
corresponds to several (e.g. 3-4) microcapsules 145 in
charge-responsive layer 139 of e-paper structure 132, as
represented in at least FIGS. 3A-3B. In one aspect, the deposited
charges 39 (that correspond to formation of one black dot 382B
(FIG. 4B)) correspond to at least the microcapsules 145 (or
portions of microcapsules) within target zone Z in FIG. 3A.
FIG. 5 is a diagram 400 including a side sectional view
schematically representing an e-paper structure 402, according to
an example of the present disclosure. In one example, the e-paper
structure 402 is consistent with, and/or includes at least some of
substantially the same features and attributes as e-paper structure
132, as previously described in association with at least FIG. 3A.
However, in diagram 400 the conductive paths 185 within
charge-receiving layer 138 extend at an angle (.alpha.) relative to
a vertical plane V, which is also represented by the line segment
A-B. Plane V extends generally perpendicular to a longitudinal axis
A3 of charge-receiving layer 139 and A2 of charge-receiving layer
138. In one aspect, line segment A-C generally corresponds to a
length of an angled conductive path 185 while line segment A-B
corresponds to a height (H2) of the charge-receiving layer 138. In
another aspect, FIG. 5 shows line segment B-C, which corresponds to
a lateral distance from the vertical plane V to an end 405B of an
angled conductive path 185.
The distance of line segment B-C corresponds to a lateral deviation
in the placement of a charge at the charge-responsive layer 139
that occurs due to the conductive paths 185 being formed at the
angle (.alpha.) instead of generally parallel to the plane V.
As further described below, at least an adequate resolution is
maintained in the resolution of an image despite a small lateral
deviation (as represented by line segment B-C) in charge placement
when the conductive paths 185 are formed with a slight non-vertical
angle. In one example, assuming a configuration including a
thickness (H2 or line segment A-B) of charge-receiving layer 138 of
150 .mu.m and an angle (.alpha.) of 5 degrees from plane V, a
lateral deviation (line segment B-C) of about 13 .mu.m would occur.
Given a dot-to-dot spacing of 84 .mu.m between imageable "dots"
(having a diameter of about 80 to 100 .mu.m) provided via writing
module 160 (FIG. 3A), a lateral deviation of about 13 .mu.m at the
charge-responsive layer 139 is generally acceptable for 300 dpi
imaging.
In some examples, as previously described in association with at
least FIG. 1A, a combined conductivity of all the conductive paths
32 in charge-receiving layer 138 is at least one order of magnitude
greater than the conductivity (.sigma..sub.body) of insulative
matrix 33. Moreover, in some examples, a first ratio of this
combined conductivity (of all the conductive paths 32) relative to
the conductivity of the insulative matrix 33 is proportional to a
second ratio of a thickness of the charge-receiving layer 138
relative to a maximum allowable lateral travel (e.g. lateral
deviation represented by line segment B-C in FIG. 5) of a charge in
the insulative matrix 33.
In some examples, these relationships exhibited within a
charge-receiving layer 138 are further represented by the equation:
d.sub.Z/d.sub.XY.about.vd.sub.Z/vd.sub.XY.about..sigma..sub.Z/.sigma..sub-
.XY.about..sigma..sub.XY/.sigma..sub.Z, where XY represents an XY
plane, Z represents a Z axis orthogonal to the XY plane, where d
represents a traveled distance, vd represents a drift velocity of
charges, G represents conductivity, and p represents
resistivity.
Accordingly, in some examples, to achieve a lateral deviation less
than 10 .mu.m then the charge-receiving layer 138 will exhibit a
resistivity ratio (.rho..sub.XY/.rho..sub.Z) larger than 15.
FIG. 6 is diagram 420 including a side sectional view of an e-paper
structure 432, according to one example of the present disclosure.
In one example, the e-paper structure 432 is consistent with,
and/or includes at least some of substantially the same features
and attributes as, e-paper structure 132 (as previously described
in association with at least FIG. 3A), except with e-paper
structure 432 having conductive paths 441 formed from spaced apart
segments 442A, 442B, 442C instead of a conductive path 185 formed
as a single elongate pattern that extends the full thickness (H2)
of the charge-receiving layer 138, as in at least FIG. 3A.
In particular, for comparison purposes, in the example of
charge-receiving layer 138 of FIG. 3A, a single conductive path 185
generally provides a single elongate pattern of conductive
particles 58 to convey (i.e. facilitate passage) of charges through
the entire thickness of the charge-receiving layer 138. However, in
the example of e-paper structure 432 shown in FIG. 6,
charge-receiving layer 438 includes a plurality of generally
parallel, spaced apart elongate conductive paths 441, with each
path 441 including a series of two or three (or more) conductive
segments of field-aligned conductive particles. As shown in FIG. 6,
some elongate conductive paths 441 include three separate or
distinct segments 442A, 442B, 442C aligned in generally end-to-end
configuration (with some lateral spacing) and that, in some
examples, function as a single elongate conductive path 441 to
facilitate passage of charges through charge-receiving layer 138.
FIG. 6 illustrates that, in some examples, a first segment 442A has
a height H4 and that a second segment (or a combination of a second
segment 442B and third segment 442C) has a height H3, with a sum of
H3 and H4 generally corresponding to the total height (H2) of
charge-receiving layer 438.
As further shown in the enlargement portion (labeled E) in FIG. 6,
in some examples, an end 443 of one segment 442B is vertically
spaced apart from (i.e. forms a gap relative to) an end 443 of an
adjacent segment 442C by a distance (D9) while the end 443 of one
segment 442B is horizontally spaced apart from (i.e. forms a gap
relative to) the end of adjacent segment 442C. In one aspect,
enlargement portion E further illustrates that each segment is
formed from an elongate pattern of conductive particles 188. In
some examples, the distance D8 and distance D9 is no greater than
10 percent of a length of one of the respective segments 442B,
442B. Given a reasonably small spacing, charges are able to travel
through charge-receiving layer 438 by jumping such vertical gaps
and/or horizontal gaps. In one aspect, the arrangement of a
conductive path 441 (as a series of separate segments 442A, 442B,
442C) demonstrates that elongate patterns of conductive particles
for conveying charges need not be formed into homogeneous
conductive paths each having a uniform shape, length, position in
order for conveying charges. Nevertheless, the arrangement of
elongate conductive paths 441 in e-paper structure 432 (FIG. 6)
does maintain generally parallel, spaced apart paths of
preferential conductivity within an insulative matrix 433.
In some examples, the multiple, spaced apart segments forming
elongate conductive paths 441 in FIG. 6 aids in preventing
attempted tampering with a written image on the charge-responsive
layer 139, such as might be attempted via a charged stylus of
pointed electrode, because any unwanted electrical charges from
these contact-based electrical sources would be limited to
traveling just the first segment (e.g. 442A) nearest the surface
192. However, in some examples, the free charges deposited by the
external writing module 160, in at least some examples of the
present disclosure, would be free to jump along the segments 442A,
442B, and 442C to reach the charge-responsive layer 139.
FIG. 7 is a diagram 460 including a side sectional view of an
e-paper structure 462, according to one example of the present
disclosure. In one example, the e-paper structure 462 is consistent
with, and/or includes at least some of substantially the same
features and attributes as, e-paper structure 432 (FIG. 6), except
with e-paper structure 462 having elongate conductive paths 481
provided via spaced apart, separate segments 482A, 482B that, when
combined in series, do not extend the full height H2 of the
charge-receiving layer 488. In particular, the elongate conductive
paths 481 are formed from one segment 482 or from two generally
end-to-end segments 482A, 482B with each elongate conductive path
481 having a height H5 that is less than the full height H2 of
charge-receiving layer 488. In this configuration, a top portion
485 of charge-receiving layer 488 generally does not include any
preferential conductive segments and has a height H6. In one
aspect, in this configuration the deposited charges 39 are not
subject to preferential conductive pathways within charge-receiving
layer 488 until the charges 39 have traveled through top portion
485, and then the charges 39 are conveyed through one of the
generally parallel, spaced apart elongate conductive paths 481.
In one aspect, this configuration achieves preferential conductive
passage of charges 39 while consuming a lower volume of particles
than configurations having full height conductive paths, such as
conductive paths 185 in FIG. 3A. In addition, the top portion 485
inhibits image disruptions from unintentional or malicious
electrical insults because the end 484 of the elongate conductive
paths 481 is not directly accessible at surface 192. Moreover,
despite the generally insulative nature of the matrix 433 forming
top portion 485, enough conductivity is present for charges
deposited at surface 192 to migrate to top end 484 of segments
482A.
FIG. 8 is a diagram 490 including a side sectional view of an
e-paper structure 492, according to one example of the present
disclosure. In one example, the e-paper structure 492 is consistent
with, and/or includes at least some of substantially the same
features and attributes as, e-paper structure 482 (as previously
described in association with at least FIG. 7), except with a
separate top portion 494 that omits preferentially conductive
segments 481. In one aspect, charge-receiving layer 491 has a
height H5, which is less than the full height H2 with top portion
494 having a height H6. In some examples, charge-receiving layer
491 includes at least substantially the same features and
attributes as charge-receiving layers 138 (FIG. 3A) or
charge-receiving layer 438 of FIG. 6.
In one aspect, the top portion 494 is made of a material different
than the insulating matrix 433 (i.e. conductive-resistant medium)
of charge-receiving layer 491. This different material in top
portion 494 provides scratch resistance, toughness, and strength
while still permitting deposited charges to pass through top
portion 494, while still on target, to be conveyed via the elongate
conductive paths 481 extending through insulative matrix 433 of
charge-receiving layer 491.
In some examples, the material forming top portion 494 exhibits
greater strength, toughness, etc. than the material forming
insulative matrix 433. In some examples, the material forming top
portion 494 has a greater degree of conductivity than insulative
matrix 433 to facilitate passage of deposited charges until the
charges reach end 484 of an upper segment 482A of the elongate
conductive paths 481.
FIG. 9 is a flow diagram schematically representing a method 600 of
manufacturing a coating for an e-paper structure, according to an
example of the present disclosure. In some examples, the method 600
is consistent with, and/or includes at least some of the
components, materials, configurations, as previously described in
association with FIGS. 1A-8, and/or method 600 can be applied to
manufacture at least some of the components, materials, and
configurations provided in association with FIGS. 1A-8.
As shown in FIG. 9, method 600 includes (at 602) forming a first
layer as coating of conductive particles dispersed within an
insulative matrix, and at 604, applying a field to cause the
conductive particles to align in generally parallel, spaced apart
elongate patterns that are generally perpendicular to a plane
through which the first layer extends. At 606, method 600 includes
curing, at ambient temperatures and without applied pressure, the
first layer via radiation energy while maintaining the applied
field.
In some examples, the particles are magnetically responsive and the
field is a magnetic field.
In some examples, the method 600 further includes providing a
substrate as an e-paper assembly having a first side comprising an
electrically passive, charge-responsive layer and an opposite
second side comprising a counter electrode layer, as shown at 620
in FIG. 10. In one aspect, the first layer is formed onto, or
transferred onto, the first side of the e-paper assembly.
In some examples, other forms of substrates are used prior to
formation of the final e-paper structure including a
charge-receiving layer.
Further details regarding the manufacture of a protective coating
layer according to at least some examples of the present disclosure
are provided below.
In some examples, during preparation of the first layer, such as a
charge-receiving layer (e.g. 40 in FIG. 1B, 138 in FIG. 3A), an
insulative matrix (33 in FIG. 1B) is selected to provide an
electrical resistance >10.sup.12 .OMEGA.-cm. In some examples,
the electrical resistance of the insulative matrix is at least
10.sup.6 to 10.sup.9 Ohms. In some examples, the electrical
resistance of the insulative matrix is 10.sup.9 to 10.sup.12
Ohms.
In some examples, the insulative matrix and conductive particles
(FIG. 3A) are selected such that the resistance ratio
(.rho..sub.metal/.rho..sub.matrix) between the conductive particles
(such as particles 58 that form elongate patterns 56 in at least
FIG. 1B) and the insulating matrix (e.g. 33 in FIG. 1B) is greater
than 10.sup.2. At least some examples of appropriate insulative
matrix materials include, but are not limited to, any organic and
inorganic forms of mono-, co-, cyclic, block, star and random
polymers composed of urethanes, acrylates, methacrylates, silicone,
epoxies, carbonates, amides, imine, lactones, saturated linear
and/or branched hydrocarbons, unsaturated and/or branched olefins,
and aromatics. In some examples, these examples include epoxies and
silicone rubbers.
With this in mind, in at least some examples, the insulative matrix
is made at least partially from a semi-conductive material and/or
materials having charge-dissipative qualities. Accordingly, the
insulative matrix is considered to be substantially insulative and
is not, strictly speaking, an absolute electrical insulator.
Rather, the insulative matrix of the charge-receiving layer is
considered substantially insulative because it is insulative
relative to the conductive paths (of elongate patterns of
conductive particles), but is otherwise not a strict insulator.
In one aspect, such polymers are curable from liquid (viscosity
ranging from 10 cP.about.10,000 P) to solid (hardness range from
shore A-D), with or without color, using radiation energy in any
wavelengths at ambient temperatures and without pressure. In one
example, the polymers are UV-curable and the applied radiation
energy falls within the UVA-UVB range.
In some examples, the conductive particles (e.g. particles 58 in
FIG. 1B, 188 in FIG. 3A) include any materials that respond to a
magnetic field. In some examples, these magnetically-responsive
materials are diamagnetic, paramagnetic, ferromagnetic,
ferromagnetic, or antiferromagnetic. In some examples, the
material(s) forming the particles 58, 188 are electrically
conductive or semi-conductive provided that the particles 58, 188
exhibit conductivity that is significantly greater than the
conductivity of the insulative matrix (i.e. conductive-resistant
medium). In one example, the particles 58, 188 exhibit conductivity
that is at least two orders of magnitude (e.g. 10.sup.2) greater
than the conductivity of the insulative matrix. In some examples,
materials suitable to serve as conductive particles (e.g. 58, 188,
etc.) generally include, but are not limited to, pure transition
metals, pure lanthanides, transition metal oxides, lanthanide
oxides, and complexes of metals from the transition metals and
lanthanides. In some examples, the conductive particles are made
from pure forms of metals selected from the group including Nickel,
Neodymium, Iron, Cobalt, and magnetite (Fe.sub.3O.sub.4), or made
from oxides or complexes of Nickel, Neodymium, Iron, Cobalt, and
magnetite.
In some examples, the conductive particles have a maximum dimension
no greater than 50 .mu.m. In some examples, the conductive
particles have a maximum dimension no greater than 10 .mu.m. In
some examples, the conductive particles have a maximum dimension no
greater than 5 .mu.m. In some examples, the conductive particles
have a maximum dimension no greater than 1 .mu.m. In some examples,
the conductive particles have a maximum dimension no greater than
100 nanometers. It will be understood that, in this context,
maximum dimension refers to a maximum dimension in any orientation
(e.g. length, width, depth, height, diameter, etc.). In some
examples, the particles vary in size within a given elongate
pattern, which in some instances, facilitates formation of the
elongate patterns. In some examples, at least some of the particles
have an aspect ratio of 1, which in some instances, facilitates
their alignment into elongate patterns, unlike other types of
conductive elements such as rods having a high aspect ratio
(length/width), which can hinder alignment when subjected to a
field at least due to physical interference of the rods with each
other.
Once the appropriate materials are gathered as described above, an
anisotropic conductive coating is prepared according to one of
several non-limiting examples described below. In some examples,
the conductive particles are dispersed directly within the
insulative matrix. In some examples, the conductive particles are
dispersed (e.g. in a solvent) prior to mixing with the insulative
matrix. These examples are further described below.
In one example of preparation including direct dispersion,
magnetite particles (Fe.sub.3O.sub.4) are obtained and Polymer 3010
(P3010) from Conductive Compounds, Inc. of Hudson, N.H. is obtained
and used without further preparation. In one example, the magnetite
particles are obtained from a vendor, such as Sigma-Aldrich of St.
Louis, Mo. and used without further preparation.
To a clean container, 0.28 g of magnetite (i.e. Fe.sub.3O.sub.4)
and 2.5 g of the P3010 polymer are combined into a mixture. In some
examples, 15 g of 3 mm zirconia beads are then introduced to the
mixture to facilitate dispersion of the magnetite during milling.
The charged container was then subjected to centrifugal milling in
a tool such as Speed mixer for increments of 30 seconds until the
resulting mixture was homogenous, such as when the mixture produces
a reading of greater than 7 on a Hegman gauge.
In one example of preparation, Nickel particles are obtained and
Polymer P15-7SP4 from MasterBond of Hackensack, N.J. is obtained
and used without further preparation. In one example, the Nickel
particles are obtained from a vendor, such as Sigma-Aldrich of St.
Louis, Mo.
To a clean container, 0.5 g of Nickel and 3.5 g of the P15-7SP4
polymer are combined into a mixture. The charged container was then
subjected to centrifugal milling in a tool such as Speed mixer for
increments of 30 seconds until the resulting mixture was
homogenous, such as when the mixture produces a reading of greater
than 7 on a Hegman gauge.
In one example of preparing an anisotropic conductivity coating,
particles are pre-dispersed in a compatible solvent via sonication,
milling, speed mixing, or micro-fluidization. In some examples,
non-impact dispersion methods are used to reduce additional steps
to remove milling media. In some examples, a typical procedure
includes charging a container with isopropanol with 15-50%
particles by weight. After this dispersion, the liquid/slurry is
then incorporated into a polymer matrix. The resulting mixture is
then subject to rotary evaporation to remove the isopropanol.
In some examples, further preparation of the anisotropic
conductivity solution includes evacuating the mixture to remove any
air that is incorporated during processing. In some examples, the
prepared mixture is subjected to vacuum (<0.05 mBar) until
completely out-gassed. The resulting mixture is then ready for
deposition as a film.
Using the out-gassed, prepared solution, in some examples a film is
prepared on any substrate directly. In some examples, releasing
substrates are used to produce free films on glass or glass-coated
substrate. In some examples, prior to receiving a film, a substrate
is prepared with a releasing agent such as silicone grease.
With this in mind, in some examples the anisotropic conductive film
is prepared onto a substrate and then transferred onto a
charge-responsive layer of an e-paper structure. In some example,
the anisotropic conductive film is deposited directly onto a
charge-responsive layer (e.g. an electrically passive, imageable
layer) of an e-paper structure.
In some examples, an anisotropic conductivity film is deposited
onto a substrate via one of several different deposition methods.
In some examples, such deposition methods include, but are not
limited to, drawn-down coating, spin-coating, guided spreading, or
roll coating. Once the desired thickness is achieved, the film is
carefully brought to a magnetic field with the appropriate field
alignment to cause alignment of the magnetically-responsive
particles to form the previously-described elongate patterns, which
serve as conductive pathways.
Once the desired "elongate conductive path" configuration is
established, this configuration (while still being subject to the
magnetic field) is then further subjected to curing with the
appropriate energy wavelengths (i.e. infrared (IR), e-beam, or
ultra-violet (UV)) to solidify the matrix with the elongate
conductive path arrangement.
In some examples, the width or diameter of the elongate conductive
paths (e.g. 56 in FIG. 1B, 185 in FIG. 3A, 441 in FIG. 6 etc.)
and/or spacing between such elongate conductive paths is
controllable via varying the viscosity of the insulative matrix
(e.g. 33 in FIG. 1B, 3A or 433 in FIG. 6), the materials used,
and/or the size of the conductive particles (e.g. 58 in FIG. 1B,
188 in FIG. 3A, etc.).
In some examples, instead of the above-described examples of
providing magnetically-responsive conductive particles and aligning
them with a magnetic field, the conductive particles are provided
with a dielectric constant that differs greatly from a dielectric
constant of the insulative matrix and an electric field is used to
align the conductive particles into elongate patterns to provide
elongate conductive paths similar to those previously described in
association with at least FIGS. 1A-8. In some examples, an electric
field is applied to a system including a dielectric matrix (polymer
in uncured state) and conducting particles, in which the conducting
particles would tend to arrange in vertical paths to reduce local
fields.
At least some examples of the present disclosure provide for a
protective coating for an electrically passive, e-paper structure
with the protective coating providing preferential conductive paths
to facilitate passage of air-borne charges to the imageable layer
of the e-paper structure.
Although specific examples have been illustrated and described
herein, a variety of alternate and/or equivalent implementations
may be substituted for the specific examples shown and described
without departing from the scope of the present disclosure. This
application is intended to cover any adaptations or variations of
the specific examples discussed herein. Therefore, it is intended
that this disclosure be limited only by the claims and the
equivalents thereof.
* * * * *
References